Pick mechanism

ABSTRACT

A pick mechanism located on one side of a paper tray includes a plurality of gears, linkage bars and a pickup roller to form a mechanism with a high degree of freedom. The pickup roller may be driven to rotate in the direction of paper feeding to generate a torque to apply a force on the top sheet of the paper tray and provide an automatic compensation for the pickup force. Furthermore, the mechanism is simply structured to save cost and space.

FIELD OF THE INVENTION

[0001] The invention relates to a pick mechanism for paper andparticularly to a pick mechanism that has a simple structure and savesspace.

BACKGROUND OF THE INVENTION

[0002] With ever changing of digital technologies, many electronicproducts have become very popular. The advance of technologies alsomakes these electronic products more compact and miniaturized. Inaddition, functional integration also has become a trend and an appealin the market place.

[0003] In the office environments, it is very common to integratebusiness machines such as a printer, copier, and FAX machine to become aMulti-Function Peripheral (MFP) that combines the functions of copying,printing, facsimile and scanning. Whether single function or multiplefunctions, the process of miniaturization has to rearrange andreorganize the physical structure. In these products, a paper conveyingmechanism, including a paper picking and transfer mechanism, has to besimplified.

[0004] In general, the paper conveying mechanism used in the copiers,printers or FAX machines usually has two rubber rollers with a greaterfriction coefficient. One is a pickup roller and the other is a feedroller. The top sheet of a paper is first separated by the pickuproller, and then is transported by the feed roller to the printingmodule for printing. The driving power source usually is located betweenthe two rubber rollers. A transmission element such as a gear set orbelt is used to transmit the driving power to the two rollers.

[0005] For the pick mechanism that uses the pickup roller to fetchpaper, the gear to transmit power will generate friction and result inenergy loss and noise. Thus, it is preferable to use as few gears aspossible. Another requirement for the pick mechanism is to preventmulti-feeds or failed feeds caused by varying of paper properties suchas weight, density or stiffness.

[0006] In order to equip the pickup roller with automatic compensatingcapability, the pickup roller usually is movable. Such a design makesthe pick mechanism more complicated. It also takes more space. Forinstance, LEXMARK Co. of U.S.A, has disclosed U.S. Pat. No. 5,527,026which has a drive roller (13) pivotally engaged on a bottom gear of agear train (1). The drive gear (3) at the front end of the gear train isstationary. The entire gear train (1) and the drive roller (13) aremovable depending on the amount of paper. The drive roller (13) is incontact with the surface of the top sheet. When all the gears in thegear train (1) rotate to drive the drive roller (13), a torque isgenerated to enable the drive roller to apply a normal force to the topsheet. The normal force alters according to the characteristics ofpaper, thus can automatically compensate the pickup force, depending onthe characteristics of paper, to avoid the problems of multi-feeds orfailed feeds.

[0007] In other words, if the drive roller is mounted on a movable endof a swinging arm (such as the gear train), the drive roller may be incontact with the top sheet all the time regardless the amount of paperin the paper tray. Meanwhile, it can increase or decrease a normalpick-up force according to the characteristics of paper.

[0008] However, the pick mechanism that adopts the swinging arm still isnot perfect. For instance, in the U.S. Pat. No. 5,527,026 assigned toLEXMARK Co., every gear in the gear train (1) is fixed relative toanother. When the entire gear train (1) is swung for paper picking, itdoes not have much space to move. Moreover, when the quantity of paperchanges (or the depth of paper tray alters), the moving path is notextended directly from the drive gear to the paper, but moves sidewardin the swinging direction. Hence, a greater space must be reserved toaccommodate the swinging of the entire gear train (1). It does not meetthe miniaturization requirement.

SUMMARY OF THE INVENTION

[0009] Therefore, the primary object of the invention is to resolve thepreviously mentioned disadvantages occurred to the conventional pickmechanisms such as bulky size, complicated structure, higher cost and aspatial design problem.

[0010] The invention provides a pick mechanism that mainly includes atransmission gear, an idling gear, a swinging arm, a pickup gear and apickup roller. The transmission gear is connected to a power inputshaft. The idling gear is engaged with the transmission gear, and theaxis of the idling gear is coupled with the power input shaft through afirst linkage bar. The pickup gear is engaged with the idling gear, andthe axis of the pickup gear is coupled with the axis of the idling gearthrough a second linkage bar. The pickup roller is located on one sideof the pickup gear and is coupled on a same pivot shaft with the pickupgear. When the power output shaft drives the transmission gear, thepower is transmitted through the idling gear and the pickup gear todrive the pickup roller to rotate in the direction of paper feeding. Thepickup roller applies a force on the top sheet of paper contained in thepaper tray to move the top sheet.

[0011] The invention aims at achieving effects such as enabling thepickup roller to compensate the pickup force automatically, simplifyingthe structure, adjusting the operation mechanism and reducing the spaceneeded.

[0012] The foregoing, as well as additional objects, features andadvantages of the invention will be more readily apparent from thefollowing detailed description, which proceeds with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a first embodiment of theinvention, with the paper tray indicated by broken lines.

[0014]FIG. 2 is a perspective view of the first embodiment of theinvention, with the paper tray and the outer frame indicated by brokenlines.

[0015]FIG. 3 is a perspective view of the first embodiment of theinvention from another side.

[0016]FIG. 4 is a side view of the first embodiment of the invention,with the side-wall of the paper tray removed.

[0017]FIG. 5 is a schematic view of the first embodiment of theinvention showing the pick mechanism in a paper pickup condition.

[0018]FIG. 6 is a schematic view of the first embodiment of theinvention showing the pick mechanism in a paper feeding condition.

[0019]FIG. 7 is a schematic view of the second embodiment of theinvention showing the pick mechanism in a paper pickup condition.

[0020]FIG. 8 is a schematic view of the second embodiment of theinvention showing the pick mechanism in a paper feeding condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Refer to FIGS. 1 through 6 for a first preferred embodiment ofthe invention. The pick mechanism 100 of the invention is located in apaper tray 200. It includes an outer frame 110, and a transmission gear120, an idling gear 130, a pickup gear 140 and a pickup roller 150located in the outer frame 110. Details of the structural andoperational relationship of the elements will be elaborated as follows.

[0022] Referring to FIGS. 1 through 4, the outer frame 110 is formed inan U-shape. It has one side fastening to a rectangular linkage block111. The linkage block 111 is fastened to an inner side of a side-wall210 of the paper tray 200. Namely, the outer frame 110 is stationary.The outer frame 110 has straight retaining slots 112 (referring toFIG. 1) and 113 (referring to FIG. 3) closed to one end, and is runthrough by a power input shaft 121. The power input shaft 121 runsthrough two side-walls 210 (only one sidewall is shown) of the papertray 200. In this embodiment, the power-input shaft 121 providesrotation power in one direction (clockwise direction, as shown in FIGS.5 and 6).

[0023] The transmission gear 120 is mounted on the power input shaft 121inside the outer frame 110 and may be driven by the power input shaft121 to rotate. As the axis of the power input shaft 121 is fixed, theaxis of the transmission gear also is fixed.

[0024] The idling gear 130 is engaged with the transmission gear 120.Its axis is coupled with the power input shaft 121 through a firstlinkage bar 160. The first linkage bar 160 is formed in a plate.

[0025] The pickup gear 140 is engaged with the idling gear 130. Its axisis coupled with the axis of the idling gear 130 through a second linkagebar 170.

[0026] The pickup roller 150 and the pickup gear 140 are coupled on thesame pivot shaft 180 and may rotate synchronously. The pivot shaft 180has one end running through the second linkage bar 170 and the retainingslot 112 of the outer frame 110 (referring to FIG. 1) and other endrunning through the retaining slot 113 (referring to FIG. 3). The pickuproller 150 is a composite structure different from the conventionalpickup roller, which has a roller surface made of a single material.Instead, the roller surface of the invention is divided into twosections. One section is a high friction surface 151, which has agreater friction coefficient, and other section is a low frictionsurface 152, which has a lower friction coefficient (referring to FIGS.3 and 4). The low friction surface 152 has two feed wheels 153. Inpractice, the lower friction surface 152 and the feed wheels 153 may bemade from hard plastics that have a smooth surface.

[0027] The structural elements and their relationship with the pickmechanism 100 are depicted as above. Referring to FIGS. 5 and 6, alsoFIGS. 1 through 4, during paper pickup process, the power input shaft121 provides rotational power (clockwise direction) to drive thetransmission gear 120, idling gear 130, pickup gear 140 and pickuproller 150 in this order. Moreover, the pickup roller 150 rotatesclockwise in the direction of the paper feeding direction 220.

[0028] In the pick mechanism 100, the idling gear 130, pickup gear 140and pickup roller 150 are movable, and the first linkage bar 160 and thesecond linkage bar 170 are swingable. Thus during operation there arefrictions between the rotating gears and the linkage bars. As a result,the first linkage bar 160 is subject to a clockwise torque 221 while thesecond linkage bar 170 is subject to a counterclockwise torque 222.Overall, the pick mechanism 100, except the stationary portions, has atendency of moving in the direction of paper 230 in the paper tray 200.In addition, the pivot shaft 180 of the pickup roller 150 and pickupgear 140 is confined in the retaining slots 112 and 113 (with theretaining slot 113 not shown in the drawings). The pickup roller 150finally will be moved downwards in a biased manner. However, it islargely moved towards the paper 230.

[0029] When the high friction surface 151 of the pickup roller 150touches the paper 230, due to the constraints of the torque 221 and 222,and the retaining slots 112 and 113, a normal force 223 will be exertedon the paper 230. And the normal force 223 will increase gradually untilthe paper 230 is moved in the direction of the paper feeding direction240. Namely, the amount of normal force 223 varies depending on theproperties of paper such as weight, density or stiffness. Therefore, itcan automatically compensate pickup force according to the properties ofpaper without the problems of multi-feeds or failed feeds. This is theso-called automatic compensation capability.

[0030] Referring to FIG. 6, when the paper 230 is moved in the paperfeeding direction for a distance D, and reaches the feed roller 300, thepickup roller 150 is also turned from the high friction surface 151 tothe lower friction surface 152 with the feed wheels 153 in contact withthe paper 230. The feed roller 300 picks up the paper 230 and moves thepaper in the paper feeding direction 240. The paper feed wheels 153merely rotate with the paper 230 without affecting the movement of thepaper 230. When the paper 230 is separated from the paper feed wheels153, the pickup roller 150 rotates to make the high friction surface 151touching the next sheet.

[0031] It is obvious that the length of the high friction surface 151 ofthe pickup roller 150 and the distance D of the paper 230 being moved tothe feed roller 300 are closely related. The length of the low frictionsurface 152 and the time for the pickup roller 150 to touch the nextsheet also are related. These factors must be adjusted duringimplementation to match the automatic control operation. Moreover, whilenot affecting the movement of the paper 230, the paper feed wheels 153may be removed. In addition, the low friction surface 152 may be formedin an arched fashion to couple with the high friction surface 151 toform a complete circular surface.

[0032] In addition, the roller surface of the pickup roller may also bean entirely high friction surface. Refer to FIGS. 7 and 8 for a secondembodiment of a pick mechanism 400 of the invention. The main differencefrom the first embodiment is that the pickup roller 410 has only a highfriction surface 411. A fine-tuning adjustment must be made for theautomatic control mechanism. During paper pickup, the power input shaft420 turns in clockwise direction to drive the pickup roller 410, movingin the paper feeding direction 510, to contact and pickup paper byrotating. Once the paper 510 arrives in the feed roller 500, the powerinput shaft 420 rotates counterclockwise to move the pickup roller 410away from the paper 510 without impeding the continuous movement of thepaper 520. Next, in this embodiment, the power-input shaft 420 mayprovide bi-directional rotations clockwise and counterclockwise, whilethe first embodiment provides only single direction rotation.

[0033] It is to be noted that the outer frame of the invention canprovide stability for the entire mechanism during operation and providea moving path for the retaining slots to confine the pickup roller.However, it is not mandatory in practice. When the outer frame isremoved, slots may be formed on the paper tray to replace the retainingslots on the outer frame to enable the coaxial pivot shaft of the pickupgear and pickup roller to couple and move to confine the moving path ofthe pickup roller.

[0034] In short, the invention is different from the conventional pickupmechanism that employs a swinging arm (such as U.S. Pat. No. 5,527,026to LEXMARK Co.). It provides a pick mechanism that has a lot of space tomove in. The total length may be directly extended according tovariation of paper content. It does not need a large space like aswinging arm mechanism, and has a simpler structure and a smaller size.It can provide an automatic compensating capability. The invention alsoprovides a novel composite pickup roller, which rotates only in onesingle direction in the paper feeding direction. Thus, driving of thepick mechanism is simpler and the complexity of automatic control isreduced.

[0035] While the preferred embodiments of the invention have been setforth for the purpose of disclosure, modifications of the disclosedembodiments of the invention as well as other embodiments thereof mayoccur to those skilled in the art. Accordingly, the appended claims areintended to cover all embodiments, which do not depart from the spiritand scope of the invention.

What is claimed is:
 1. A composite pickup roller equipped on a pickmechanism, said pick mechanism being located on one side of a papertray, comprising a plurality of gears to drive the pickup roller incontact with the top sheet of paper held in the paper tray, and rotatingin a direction of paper feeding to carry the paper towards the feedroller; wherein the pickup roller has a roller surface which includes ahigh friction surface and a low friction surface, the high frictionsurface driving the paper through a friction force, the low frictionsurface permitting the paper to slide through, and the high frictionsurface having a length which is determined by the distance between aninitial position of the paper and the feed roller.
 2. The pickup rollerof claim 1, wherein the high friction surface is made from a softrubber.
 3. The pickup roller of claim 1, wherein the low frictionsurface is made from a hard plastic to provide a smooth surface.
 4. Thepickup roller of claim 1, wherein the low friction surface has at leastone feed wheel.
 5. The pickup roller of claim 4, wherein the feed wheelis made from a hard plastic to provide a smooth surface.
 6. A pickmechanism located on one side of a paper tray, comprising: atransmission gear connecting to a power input shaft; an idling gearengaged with the transmission gear having an axis coupled with the powerinput shaft through a first linkage bar; a pickup gear engaged with theidling gear having an axis coupled with the axis of the idling gearthrough a second linkage bar; and a pickup roller located on one side ofthe pickup gear coupling on a pivot shaft with the pickup gear in acoaxial manner; wherein the transmission gear is driven by the powerinput shaft to transfer driving power through the idling gear and thepickup gear, the pickup roller rotating in the direction of paperfeeding to move a top sheet of paper in the paper tray.
 7. The pickmechanism of claim 6 further comprising a U-shaped outer frame fastenedto an inner side of the paper tray, the gears and the pickup rollerbeing located on an inner side of the outer frame.
 8. The pick mechanismof claim 7, wherein the outer frame is fastened to the inner side of thepaper tray through a linkage block.
 9. The pick mechanism of claim 7,wherein the outer frame has at least one retaining slot run through bythe pivot shaft.
 10. The pick mechanism of claim 7, wherein the outerframe is run through by the power input shaft.
 11. The pick mechanism ofclaim 6, wherein the paper tray has one side forming a slot run throughby the pivot shaft.
 12. The pick mechanism of claim 6, wherein thepickup roller has a roller surface which includes a high frictionsurface and a low friction surface.
 13. The pick mechanism of claim 12,wherein the high friction surface is made from a soft rubber.
 14. Thepick mechanism of claim 12, wherein the low friction surface is madefrom a hard plastic to provide a smooth surface.
 15. The pick mechanismof claim 12, wherein the low friction surface has at least one feedwheel.
 16. The pick mechanism of claim 15, wherein the feed wheel ismade from a hard plastic to provide a smooth surface.
 17. The pickmechanism of claim 12, wherein the power input shaft provides rotationalpower in one direction.
 18. The pick mechanism of claim 6, wherein thepickup roller has a roller surface made from a soft rubber.
 19. The pickmechanism of claim 6, wherein the power input shaft provides rotationalpower in dual directions.
 20. The pick mechanism of claim 6, wherein thefirst linkage bar and the second linkage bar are formed in a plateshape.